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Publicly Available Published by De Gruyter September 13, 2016

Nomenclature for Properties and Units or NPU Terminology

From the journal Chemistry International

Laboratory medicine has an important role in clinical decision making in healthcare everywhere. Results of sample-based patient investigations are involved in almost every decision on diagnosis or treatment and frequently make up the largest amount of data in healthcare records. Most of the results represent chemical and biochemical measurements, with increasing involvement of molecular biology.

With the advent of digital data storage and widespread communication of investigation results, new possibilities have opened for both research and patient care. The challenge is to ensure that all users have a common understanding of what is being measured, how the results are expressed, and with which unit. This demands a stable and metrological sound international standard for identifying measurement results. To support this, IUPAC and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) have partnered to publish several recommendations and supported work on the Nomenclature for Properties and Units (or NPU) terminology and its basic principles for decades.

The NPU definitions have a uniform structure and use a referenced vocabulary for every term. The outcome of a patient examination yields information about certain properties of the patient, and the NPU terminology identifies the laboratory result by specifying these properties. It follows international standards of metrology, including IUPAC Recommendations.

Today, NPU terminology is a coding system and terminology for the identification and communication of examination results, covering most fields of clinical laboratory science.

The structured definitions describe:

  1. the part of the universe that is studied (the system)

  2. the component that is examined in that system

  3. the estimated kind-of-property of the component in that system

  4. measurement unit and specifications where relevant

  5. an individual code value identifying the definition


NPU03568 B—Thrombocytes; num.c. = ? × 109/L.

  1. B - is Blood and is the part of the universe that is studied (the system)

  2. Thrombocytes is the component that is examined in the system, Blood

  3. num.c. is number concentration, the estimated kind-of-property of the component in the system

  4. 109/L is the measurement unit and specification where relevant

NPU03568 B—Thrombocytes; num.c. = 60 × 109/L - means

The number of thrombocytes per litre blood is 60 × 109

By using the NPU codes, the examination results will be:

  1. fully defined in the clinical context

  2. transferable between systems

  3. comparable to other results of the same kind

  4. reusable for decision support, calculations, research, statistics, etc.

The NPU terminology has proved useful in health informatics and health care for 15 years, and is today a National standard in Denmark, Sweden, and Norway. It is implemented in all laboratory departments at hospitals and private labs, suppliers of laboratory systems and EHRs, and National registers and databases, and is used for online requesting from the GP to the researching laboratory.

The Norwegian Directorate of eHealth has implemented the NPU terminology as a national standard for laboratories in communicating requisitions and examination results in the sector of specialized health services.

The NPU terminology has been in use in Sweden for more than 10 years and is the basis for the National Patient Summary to collect information from different healthcare systems in hospitals, GP’s, and private healthcare providers and to make the information available for all users of EHR in the country.

For further information, contact Helle Moller Johannessen <>, chair of the Subcommittee on Nomenclature for Properties and Units (SC-NPU) and member of the IUPAC Chemistry and Human Health (Div VII)

Visit the NPU website at

Online erschienen: 2016-9-13
Erschienen im Druck: 2016-9-1

©2016 by Walter de Gruyter Berlin/Boston

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